Silver bridge element slapper detonator

ABSTRACT

A slapper detonator includes a ceramic substrate, a silver bridge element attached on the substrate, electrical leads attached to the silver bridge element and the substrate, a flyer material covering the silver bridge, a spacer element attached to the ceramic substrate, an explosive pellet attached to the spacer element, electrical conductors attached to the electrical leads and a high voltage fireset attached to the electrical conductors.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

The United States Government has rights in this invention pursuant to Contract No. DE-AC52-07NA27344 between the United States Department of Energy and Lawrence Livermore National Security, LLC for the operation of Lawrence Livermore National Laboratory.

BACKGROUND

1. Field of Endeavor

The present invention relates to explosives and more particularly to a slapper detonator.

2. State of Technology

Slapper detonators are used to initiate explosives for commercial and military applications. Slapper detonators are a class of detonators that has been capturing a larger and larger share of the detonator market. The value of slapper detonators is found in the fact that these detonators can be made to fire at low energies and yet remain safe due to the unique firing requirements.

High Voltage Detonators contain small “bridges” that are exploded by the high current pulse from the fireset. The bridges can be made of different materials but the best performance is generally achieved by the best conductors. The four best conductors are in rank order, silver, copper, gold and aluminum. Early designs that required the bridgewire to be in contact with the explosive used gold because it is highly resistant to chemical attack. silver, due to its high susceptibility to chemical attack, was rejected early for this application.

Slapper detonators operate by using the exploding bridge to propel a small plastic insulating layer or “flyer” into the explosive. Because the bridge is no longer in contact with the explosive, other materials besides gold can and have been used. Silver, however, has never been tried in a slapper application, perhaps due to the early rejection.

SUMMARY

Features and advantages of the present invention will become apparent from the following description. Applicants are providing this description, which includes drawings and examples of specific embodiments, to give a broad representation of the invention. Various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this description and by practice of the invention. The scope of the invention is not intended to be limited to the particular forms disclosed and the invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims.

The present invention provides a silver bridge element slapper detonator. The silver bridge element slapper detonator includes a ceramic substrate, a silver bridge element attached on the substrate, electrical leads attached to the silver bridge element and the substrate, a flyer material covering the silver bridge, a spacer element attached to the ceramic substrate, an explosive pellet attached to the spacer element, electrical conductors attached to the electrical leads and a high voltage fireset attached to the electrical conductors.

The present invention also provides a method of making a slapper detonator, including the steps of providing a ceramic substrate, providing a silver bridge element, providing electrical leads attached to the silver bridge element, providing a flyer material covering the silver bridge, providing a spacer element attached to the ceramic substrate, providing an explosive pellet attached to the spacer element, providing electrical conductors attached to the electrical leads and providing a high voltage fireset attached to the electrical conductors. When used in this application the term “high voltage” means a voltage greater than 28 volts.

In making the present invention, Applicant went against the teachings of the prior art. Applicant's original Record of Invention (ROI) completed some time ago included the following statements: “Early designs that required the bridgewire to be in contact with the explosive used gold because it is highly resistant to chemical attack. Silver, due to its high susceptibility to chemical attack, was rejected early for this application.” The prior art taught away from the direction of the Applicant's invention.

Applicant's slapper detonator is used to initiate explosives for commercial and military applications. Slapper detonators are a class of detonators that have been capturing a larger and larger share of the detonator market. The value of slapper detonators is found in the fact that these detonators can be made to fire at low energies and yet remain safe due to the unique firing requirements.

The invention is susceptible to modifications and alternative forms. Specific embodiments are shown by way of example. It is to be understood that the invention is not limited to the particular forms disclosed. The invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and constitute a part of the specification, illustrate specific embodiments of the invention and, together with the general description of the invention given above, and the detailed description of the specific embodiments, serve to explain the principles of the invention.

FIG. 1 shows a Prior Art flying-plate detonator using a high-density high explosive system.

FIGS. 2A and 2B illustrate one embodiment of Applicants' invention.

FIG. 3 illustrates another embodiment of Applicants' invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring to the drawings, to the following detailed description, and to incorporated materials, detailed information about the invention is provided including the description of specific embodiments. The detailed description serves to explain the principles of the invention. The invention is susceptible to modifications and alternative forms. The invention is not limited to the particular forms disclosed. The invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims.

Referring now to the drawings and in particular to FIG. 1, a Prior Art flying-plate detonator using a high-density high explosive system is disclosed. The Prior Art detonator is designated generally by the reference numeral 9. This type of detonator is described and illustrated in U.S. Pat. No. 4,788,913 for a flying-plate detonator using a high-density high explosive issued to John R. Stroud and Donald L. Ornellas on Dec. 6, 1968. The disclosure of U.S. Pat. No. 4,788,913 is incorporate herein in its entirety for all purposes.

The Prior Art flying-plate detonator 9 using a high-density high explosive is illustrated in U.S. Pat. No. 4,788,913 and in FIG. 1. The flying-plate detonator 9 using a high-density high explosive includes the structural elements listed in Table 1.

TABLE 1 Component Reference Numeral backing or head 10 printed circuit board 11 upper electrode 12 dielectric substrate 13 insulation layer 14 protruding portion 15 lower electrode 16 firing lead cable 17 jumper 18 exploding foil 19 sheet 20 spacer or standoff 21 air space or bore 22 high-density explosive pellet 23 main or primary explosive 24

As illustrated in HG. 1, the Prior Art flying-plate detonator 9 using a high-density high explosive includes a flying-plate detonator including a backing or head 10 which secures therein a printed circuit board generally indicated at 11 having an overall thickness of 31 mils, for example and composed of an upper electrode 12, a suitable dielectric substrate 13, an insulation layer 14, such as Epon 828, and having a protruding portion 15, and a lower electrode 16 configured to allow protruding portion 15 of insulation layer 14 to extend therethrough and be flush therewith, electrodes 12 and 16 being made, for example, of 5 mil thick copper. The head 10 is configured so as to provide a backing surface for the printed circuit board 11 of from about 125 to 250 mils thick, for example. A firing lead cable 17 extends into head 10 and is electrically secured to one end of each of electrodes 12 and 16. A jumper 18 is secured across the other ends of electrodes 12 and 16, jumper 18 being constructed of 5 mil thick copper, for example. An exploding foil 19, of gold, for example, with a thickness of 0.1 to 0.5 mils is electrically secured to electrode 16. A sheet 20 of Mylar, or other suitable flyer material, of a thickness in the range of 2-75 mils, is secured between the exploding foil 19 and a spacer or standoff 21, which for example may be constructed of fucite or polymethyl methacrylate. Spacer or standoff 21 is provided with an air space or bore 22, which in this example is square in cross-section with a width of 60-100 mils and a length of from 5-250 mils. A high-density explosive pellet 23 of benzotrifuroxan (BTF) is secured to the standoff 21, pellet 23, for example, being 250 mils in diameter and 100 mils in length.

In operation of the FIG. 1 Prior Art flying-plate detonator 9, a large current pulse is directed through firing cable 17 and across electrodes 12 and 16 explosively vaporizing the foil or film 19 which causes a flyer or disc to be cut out of sheet 20 and driven down the bore 22 or spacer or standoff 21 striking the high-density explosive pellet 23 which explodes and detonates an associated main or primary charge 24 shown generally by the component shown in dotted lines. The length and diameter of the bore 22, and the thickness of the flyer, as described in greater detail hereinafter, is set such that the flyer from sheet 20 reaches a maximum velocity just before impacting against the pellet 23. More specifically, the area of the planar pressure shock is determined by the cross sectional area of the flyer. It is slightly greater than the minimum critical area required for positive detonation of the explosive pellet. The magnitude and duration of the pressure shock are dependent on the thickness of the flyer film or layer and the magnitude of the acceleration generated by the explosively-vaporized conductive foil.

The distance or thickness of standoff between the flyer and the explosive pellet has been varied from 0 to 250 mils. Good performance required a standoff thickness less than 40 mils. Velocity history plots show that the flyer accelerates in the interval from 5 to 20 mils, depending on design parameters, and then decelerates. Best performance is obtained if the spacing or length of bore is chosen for maximum velocity. Performance suffers at long distances due to the reduced speed and the instability of the flyer. The optimum standoff varies with firing voltage, and is thus influenced by the choice of fireset. The velocities obtained in these tests varied from less than 1 mm/.mu.sec to over 5. The high velocities were observed only with the very thin flyers. Most of the measurements were in the range from 2 to 3 mm/.mu.sec.

The confinement of the exploding foil is very important. The exploding foil can be confined either beneath the flyer film or continuous over an area large compared to the foil size or in a bore (“gun barrel”) arrangement.

Example 1

Slapper detonators are a kind of detonator wherein an expanding plasma from an explosion of a metal foil or bridgewire drives another thin plastic or metal foil called a “flyer” or a “slapper” across a gap, and its high-velocity impact on the explosive. A detonator system contains a small “bridge” that is exploded by the high current pulse from a fireset. The bridge is made of silver which provides the improved performance.

In example 1 of Applicant's slapper detonator embodiment a ceramic substrate has a silver bridge element attached on the substrate. Two electrical leads are attached to the silver bridge element. A flyer material covers the silver bridge element. A spacer element is attached to the ceramic substrate. An explosive pellet is attached to the spacer element. Electrical conductors are attached to the electrical leads and to the high voltage fireset. When the Fireset discharges through the circuit created by the electrical conductors, the electrical leads and the silver bridge element; several thousand amperes of electrical current through the silver bridge element, causing it to explode. The explosion drives the portion of the flyer material covering the silver bridge element and causes it to fly across the gap created by the spacer element. The explosive pellet detonates when the portion of the flyer material propelled by the exploding silver bridge element impacts the explosive pellet.

In making the present invention, Applicant went against the teachings of the prior art. Applicant's original Record of Invention (ROI) completed some time ago included the following statements: “Early designs that required the bridgewire to be in contact with the explosive used gold because it is highly resistant to chemical attack. Silver, due to its high susceptibility to chemical attack, was rejected early for this application.” The prior art taught away from the direction of the Applicant's invention.

Applicant's use of silver for the bridge element in the slapper detonator had unexpected results. Applicant's use of silver for the bridge element in the slapper detonator explosive provides the maximum performance for a given energy over any other bridge material. This is based on the fact that silver possesses both a high specific action as well as a low volumetric enthalpy. Silver possess a superior combination of these two characteristics than any other material.

Example 2

Example 2, representing one embodiment of Applicant's slapper detonator explosive invention, is shown in FIGS. 2A and 2B. Applicant's slapper detonator embodiment is designated generally by the reference numeral 200. Slapper detonators are a kind of detonator wherein an expanding plasma from an explosion of a metal foil or bridgewire drives another thin plastic or metal foil called a “flyer” or a “slapper” across a gap, and its high-velocity impact on the explosive. FIG. 2A is an expanded illustration of Applicant's slapper detonator explosive 200. FIG. 2B is a side of Applicant's slapper detonator explosive 200.

Referring to FIG. 2A, Applicant's slapper detonator embodiment 200 includes a ceramic substrate 201, a silver bridge element 202 attached on the substrate 201, two electrical leads 203 a and 203 b attached to the silver bridge element 202, a flyer material 204 covering the silver bridge element 202, a spacer element 208 attached to the ceramic substrate 201, an explosive pellet 209 attached to the spacer element 208, electrical conductors 205 and 206 that attached to the electrical leads 203 a and 203 b to high voltage fireset 207, and explosive pellet 209.

When the fireset 207 discharges through the circuit created by the electrical conductors 205 and 206, the electrical leads 203 a and 203 b and the bridge foil 202; several thousand amperes of electrical current through the silver bridge foil 202, causing it to explode. The explosion and drives the portion of the flyer material 204 covering the bridge and causes it to fly across the gap created by the spacer element 208. The explosive pellet 209 detonates when the portion of the flyer material 204 propelled by the exploding bridge 202 impacts the explosive pellet 209.

In making the present invention, Applicant went against the teachings of the Prior Art. Applicant's original Record of Invention (ROI) completed some time ago included the following statements: “Early designs that required the bridgewire to be in contact with the explosive used Gold because it is highly resistant to chemical attack. Silver, due to its high susceptibility to chemical attack, was rejected early for this application.” The prior art taught away from the direction of the Applicant's invention.

Applicant's use of silver for the bridge element 202 in the slapper detonator 200 had unexpected results. Applicant's use of silver for the bridge element 202 in the slapper detonator explosive 200 provides the maximum performance for a given energy over any other bridge material. This is based on the fact that silver possesses both a high specific action as well as a low volumetric enthalpy. Silver possess a superior combination of these two characteristics than any other material.

The detonator system 200 contains the small “bridge” 202 that is exploded by the high current pulse from the fireset 208. The bridge 202 is made of silver which provides the best performance. The four best conductors are in rank order, silver, Copper, Gold and Aluminum.

There are two properties that make the Silver bridge 202 the best performer. One is the Specific Action to Burst and the other is the Volumetric Enthalpy. The higher the Specific Action to Burst, the higher the current density that can be achieved at the instant the material becomes a vapor. The higher the current density, the faster the bridge can propel the flyer. Of the four conductors mentioned earlier, the rank order (highest to lowest) of Specific Action to Burst is copper, silver, gold and aluminum.

The other material property is Volumetric Enthalpy. This can be understood as the amount of energy required to heat a given amount of material from room temperature to vapor. The firing system that supplies energy to the exploding bridge, must first supply the energy to vaporize the bridge and then supply energy to heat the vapor and push the flyer. Materials with the lowest Volumetric Enthalpy requires the lowest amount of energy to vaporize leaving the maximum remaining energy for heating the vapor. Of the four conductors mentioned earlier, the rank order (lowest to highest) of Volumetric Enthalpy is silver, aluminum, gold and copper.

Example 3

An example, representing another embodiment of Applicant's slapper detonator explosive invention, is shown in FIG. 3. Applicant's slapper detonator embodiment of FIG. 3 is designated generally by the reference numeral 300. Applicant's slapper detonator embodiment 300 includes a ceramic substrate 301, a silver bridge element 302 attached on the substrate 301, two electrical leads 303 a and 303 b attached to the silver bridge element 302, and a flyer material 304 covering the bridge element 302. The silver bridge element 302 is made of pure silver.

When the fireset discharges through the circuit created by the electrical conductors 305 and 306, the electrical leads 303 a and 303 b and the bridge foil 302; several thousand amperes of electrical current through the silver bridge foil 302, causing it to explode. The explosion and drives the portion of the flyer material 304 covering the bridge and causes it to fly across a gap and detonate the explosive detonators.

Applicant's use of pure silver for the bridge element 302 in the slapper detonator explosive 300 provides the maximum performance for a given energy over any other bridge material. This is based on the fact that silver possesses both a high specific action as well as a low volumetric enthalpy. Silver possess a superior combination of these two characteristics than any other material, in the embodiment 300 the silver in the bridge element is made of substantially pure silver. In another embodiment the silver in the bridge element is made of silver that is more than 10% pure silver.

While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims. 

1. A slapper detonator apparatus, comprising: a substrate, a silver bridge element positioned on said substrate, a first electrical lead attached to said substrate and said silver bridge element, a second electrical lead attached to said substrate and said the silver bridge element, a flyer material positioned on and covering said silver bridge element, a spacer positioned over said substrate and said flyer material, an explosive pellet positioned over said spacer said flyer material and said substrate, a first electrical conductor attached to said first electrical lead, a second electrical conductor attached to said second electrical lead, and a high voltage fireset attached to said first electrical lead and said second electrical lead.
 2. A slapper detonator apparatus, consisting of: a substrate, a silver bridge element positioned on said substrate, a silver bridge element positioned on said substrate, a first electrical lead attached to said substrate and said silver bridge element, a second electrical lead attached to said substrate and said the silver bridge element, a flyer material positioned on and covering said silver bridge element, a spacer positioned over said substrate and said flyer material, an explosive pellet positioned over said spacer said flyer material and said substrate, a first electrical conductor attached to said first electrical lead, electrical lead, a second electrical conductor attached to said second electrical lead, and a high voltage fireset attached to said first electrical lead and said second electrical lead.
 3. The slapper detonator apparatus of claim 2, wherein said silver bridge element is made of silver that is more than 10% pure silver.
 4. A slapper detonator apparatus, comprising: a substrate, a silver bridge element made of silver that is more than 99% pure silver attached to said substrate, a first electrical lead positioned on said substrate and said silver bridge element, second lead attached to said substrate and said the silver bridge element, a flyer material positioned on and covering said silver bridge element, a spacer positioned over said substrate and said flyer material, an explosive pellet positioned over said spacer said flyer material and said substrate, a first electrical conductor attached to said first electrical lead, a second electrical conductor attached to said second electrical lead, and a high voltage fireset attached to said first electrical lead and said second electrical lead.
 5. The slapper detonator apparatus of claim 4 wherein said silver bridge element has a rectangle shape with two long sides and two short sides and wherein said first electrical lead has a trapezoid shape with a small side and wherein said small side of said trapezoid shape is attached to one of said short sides of said silver bridge element.
 6. The slapper detonator apparatus of claim 4 wherein said silver bridge element has a rectangle shape with two long sides and two short sides and wherein said second electrical lead has a trapezoid shape with a small side and wherein said small side of said trapezoid shape is attached to one of said short sides of said silver bridge element.
 7. The slapper detonator apparatus of claim 4 wherein said first electrical lead is made of silver.
 8. The slapper detonator apparatus of claim 4 wherein said second electrical lead is made of silver.
 9. The slapper detonator apparatus of claim 4 wherein said substrate has a flat surface and said silver bridge element made of silver that is more than 10% pure silver is attached to said flat surface of said substrate.
 10. A slapper detonator apparatus, consisting of: a substrate, a silver bridge element made of silver that is more than 99% pure silver positioned on said substrate, a first electrical lead positioned on said substrate and said silver bridge element, a second electrical lead attached to said substrate and said the silver bridge element, a flyer material positioned on and covering said silver bridge element, a spacer positioned over said substrate and said flyer material, an explosive pellet positioned over said spacer said flyer material and said substrate, a first electrical conductor attached to said first electrical lead, a second electrical conductor attached to said second electrical lead, and a high voltage fireset attached to said first electrical lead and said second electrical lead.
 11. A method of making a slapper detonator, comprising consisting of the steps of: providing a substrate, positioning a silver bridge element on said substrate, connecting a first electrical lead attached to said substrate and said silver bridge, connecting a second electrical lead attached to said substrate and said silver bridge, positioning a flyer material on and covering said silver bridge element, positioning a spacer over said substrate and said flyer material, positioning an explosive pellet over said spacer said flyer material and said substrate, connecting a first electrical conductor attached to said first electrical lead, connecting a second electrical conductor attached to said second electrical lead, connecting a high voltage fireset attached to said first electrical lead and said second electrical lead.
 12. The method of making a slapper detonator of claim 11 wherein said steps of providing positioning a silver bridge element on said substrate comprises positioning a silver bridge element made of silver that is more than 10% pure silver on said substrate.
 13. A method of making a slapper detonator, comprising the steps of: providing a substrate, positioning a silver bridge element that is more than 10% pure silver on said substrate, connecting a first electrical lead attached to said substrate and said silver bridge, connecting a second electrical lead attached to said substrate and said silver bridge, positioning a flyer material on and covering said silver bridge element, positioning a spacer over said substrate and said flyer material, positioning an explosive pellet over said spacer said flyer material and said substrate, connecting a first electrical conductor attached to said first electrical lead, connecting a second electrical conductor attached to said second electrical lead, connecting a high voltage fireset attached to said first electrical lead and said second electrical lead.
 14. The method of making a slapper detonator of claim 13 wherein said steps of positioning a silver bridge element that is more than 10% pure silver on said substrate comprises positioning a silver bridge element that is more than 10% pure silver and has a rectangle shape with two long sides and two short sides on said substrate and wherein said first electrical lead has a trapezoid shape with a small side and wherein said small side of said trapezoid shape is attached to one of said short sides of said silver bridge element.
 15. The method of making a slapper detonator of claim 13 wherein said steps of connecting a first electrical lead attached to said substrate and said silver bridge comprises connecting a first electrical lead made of silver attached to said substrate and said silver bridge.
 16. The method of making a slapper detonator of claim 13 wherein said steps of connecting a first electrical lead attached to said substrate and said silver bridge comprises connecting a second electrical lead made of silver attached to said substrate and said silver bridge. 